JPH10322561A - Color transformation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prepare the images of a hard copy capable of obtaining the visual feeling of the same color tone for the color image information of a monitoring device by changing the chromaticity value of the gray axis of the three attribute coordinate of colors by the brightness of the color image information and transforming the color image information to control signals by the value. SOLUTION: A unit color space cube including the color image information input coordinate value of the monitoring device is selected, linear interpolation is performed by an output value corresponding to the cube vertex and an input coordinate value and the output value corresponding to the printer control signal C, M, Y and K values are obtained. In the same color tone as a monitoring device display color on a color hard copy, a correction value corresponding to vertex data are transformed to the printer control signal C, M, Y and K values and stored in a ROM 2 for a vertex output value, it is referred to, the C, M, Y and K values are arithmetically interpolated respectively in a processing part 5a for C for computing the C value, the processing part 5b for M for computing the M value, the processing part 5c for Y for computing the Y value and the processing part 5d for K for computing the K value in an interpolation processing part 5 and the printer control signals are obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention converts color image information of a monitor device which displays a color image by a light source color displayed on a TV or CRT monitor into a control signal of an image forming apparatus for forming a color hard copy. The present invention relates to a color conversion device.

[0002]

2. Description of the Related Art When a hard copy of a color image displayed on a monitor device such as a TV or a CRT is formed on a color recording material, the color temperature of the light source for observing the hard copy is different from the color temperature of the monitor device. In contrast, in general, the color temperature of the light source for observing the hard copy is lower, and there is also a difference in the visual perception between the light source color and the reflected color. There is a problem that a hard copy having a color different from the color image is formed.

In order to solve this problem, Japanese Patent Laid-Open Publication No. 1-2
In Japanese Patent No. 18288, when a color image displayed on a color TV is hard-copied on a color recording material, tristimulus values of colors of the color TV color image under a hard copy observation light source are obtained, and these tristimulus values are obtained. A method for forming a color hard copy in which a hard copy is recorded on a color recording material so as to realize the above is disclosed.

[0004]

In the method for forming a color hard copy according to the disclosure, when the color hard copy observation light source is a reference white color TV, the color hard copy is adapted to the reference white color. It is assumed that the color of the light source is substantially the same as the color of the original light source of the color TV. Certainly, for high-saturation colors, the human eye perceives the color relative to the reference white, so it adapts to the white color of the light source when observing a color hardcopy. The difference in color tone is conspicuous for colors, and in particular, for natural images such as photographs, the visual impression of the color of a color TV image differs from that of a hard copy. On the other hand, when a color TV image is reproduced as it is by hard copy, a color which should be originally white is reproduced with a bluish tint.

SUMMARY OF THE INVENTION The present invention has been made in view of the current situation of a color conversion apparatus for converting color image information of a monitor device into a color copy image as described above. Is to provide a color conversion apparatus capable of creating a hard copy image that can provide the same color tone visual feeling.

[0006]

According to one aspect of the present invention, there is provided an image forming apparatus for forming a color hard copy of color image information of a monitor device which displays a color image by a light source color. Changing means for changing the chromaticity value of the gray axis of the three attribute coordinates of the color in accordance with the brightness of the color image information; and a chromaticity value changed by the changing means. And converting means for converting the color image information into the control signal based on the control information.

According to another aspect of the present invention, a color image information of a monitor device displaying a color image by a light source color is transmitted to a control signal of an image forming apparatus for forming a color hard copy. A color conversion device for converting, wherein a reference white color of the color image of the monitor device is set to a ground white color of a recording medium on which the color hard copy is formed, and a black color of the color image of the monitor device is the color hard copy. According to the brightness of the color image information, tilt the gray axis of the three attribute coordinates of the color so that the virtual hard copy of the chromaticity value having the same hue as the reference white under the light source to observe is set to black. Changing means for changing the chromaticity value by the control means, and converting means for converting the color image information into the control signal based on the chromaticity value changed by the changing means. The one in which the features.

According to another aspect of the present invention, a color image information of a monitor device for displaying a color image by a light source color is transmitted to a control signal of an image forming apparatus for forming a color hard copy. A color conversion device for converting, wherein a reference white color of the color image of the monitor device is set to a ground white color of a recording medium on which the color hard copy is formed, and a black color of the color image of the monitor device is the color hard copy. According to the brightness of the color image information, tilt the gray axis of the three attribute coordinates of the color so that the virtual hard copy of the chromaticity value having the same hue as the reference white under the light source to observe is set to black. Changing means for changing the chromaticity value, and a compression means for compressing the color image information based on the chromaticity value changed by the changing means,
The input coordinates of the color image information compressed by the compression means with respect to the three-dimensional input color space having an achromatic color axis and divided into the same unit color space cube, the unit color space including the input coordinates An interpolation operation means for obtaining the control signal by performing an interpolation operation based on a vertex output value of a color separation component set at a vertex of a cube.

[0009] Similarly, in order to achieve the above object, a fourth aspect of the present invention is the same as the third aspect, except that a selection setting means for selecting and setting the chromaticity value of the virtual hard copy is provided. It is characterized by having.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION

[First Embodiment] A first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is an explanatory diagram of an RGB space used for an input color space of the present embodiment, FIG. 2 is a block diagram showing a configuration of a main part of the present embodiment, FIG. 3 is an explanatory diagram of processing of the present embodiment, FIG. 4 is an explanatory diagram of color correction according to the present embodiment.

In this embodiment, as shown in FIG.
A three-dimensional input color space in which input coordinates of color image information of a monitor device that displays a color image by a light source color, such as a V or CRT monitor, is set as an RGB color space, and the RGB color space has the same unit color It is divided into spatial cubes, and the input coordinate values (R
The C, M, Y, and K values, which are control signals of the printer, are obtained from the RGB color space as output values for the RGB values. In this case, a unit color space cube including the input coordinate values of the color image information of the monitor device is selected, and linear interpolation is performed based on the output values corresponding to preset vertices of the selected unit color space cube and the input coordinate values. Are performed, and C, M,
The output values corresponding to the Y and K values are configured to be obtained.

In this embodiment, as shown in FIG. 2, a ROM 1 in which output values (C, M, Y, K) corresponding to vertices of an input color space are stored in advance in a CPU 1 for controlling the entire operation.
2, based on the RAM3 in which the input image data is temporarily stored, and the data stored in the ROM2 based on the input signal,
An interpolation operation unit 5 for performing an interpolation operation on the C, M, Y, and K values is connected. The interpolation calculation unit 5 includes a C processing unit 5a for calculating a C value, an M processing unit 5b for calculating an M value, a Y processing unit 5c for calculating a Y value, and a K processing for calculating a K value. A portion 5d is provided.

First, the process of determining the output values (C, M, Y, K) for the vertices (RGB) of the input color space stored in the ROM 2 will be described. As shown in FIG. 3, in the conversion process 10, the vertices (RGB) of the unit color space cube are converted into tristimulus values XYZ. This conversion includes a method of displaying the RGB colors corresponding to the vertices on the target monitor device and directly measuring the colors, and a method of calculating the following formula using the chromaticity coordinates of the phosphor of the monitor device. .

X = (xR / yR) L (vR) + (xG / yG) L (vG) + (xB / yB) L (vB) Y = L (vR) + L (vG) + L (vB) Z = (ZR / yR) L (vR) + (zG / yG) L (vG) + (zB / yB) L (vB) (1) where xa, yb, za (a) = R,
G, B) are chromaticity coordinates of the phosphor, L (va), (a = R,
G and B) are luminance values.

Next, in a conversion step 11, the tristimulus values X, Y, and Z are converted into CIELab, which is a representative uniform color space, by the following equation.

L * = 116 (Y / Y0) 1/3 -16 a * = 500 [(X / X0) 1/3-(Y / Y0) 1/3] b * = 200 [(Y / Y0) 1/3-(Z / Z0) 1/3] (2) where Y / Y0> 0.00885 in the expression (2).
6, X0, Y0, and Z0 are values of the reference reflecting surface.

Here, in the case of an object color such as a hard copy, L * falls within the range of 0 to 100. However, since there is no upper limit for the input of the light source color of the monitor device, the value X0 of the reference reflection surface is not determined. , Y0, and Z0 are used as tristimulus values of the reference white in the target monitor device.

As described above, in the target monitor device, the vertex data converted into L, a, and b on the basis of white is displayed on the color hard copy in the color conversion process 12 on the monitor device. The color is corrected so as to have the same color as the color. In the present embodiment, the vertex data L, a, and b are corrected according to L (brightness) obtained in step 11 based on the correction values L'ah, bh for the input L as shown in FIG. . For example, vertex data L; 5
When 0, a; 30, b; -30 are input, the following interpolation calculation is performed.

Ah = −2 + (0 − (− 2)) / (60−)
50) / (60-40)) =-1 bh = -6 + (-4-(-6)) / ((60-50) /
(60-40)) =-5

From these results, L ', a',
b 'is required.

L ′ = 40 + (50−40) / ((60−50) / (60−40)) = 45 a ′ = 30 + ah = 30−1 = 29 b ′ = − 30 + bh = −30−5 = − 35 ... (3)

The correspondence shown in FIG. 4 is such that C and C are such that the display of gray (L = 0 to 100, a = b = 0) of the target monitor device and the output color of the printer have the same color. Colorimetry is performed for the combination of M, Y, and K, and the color is set in advance.

Then, in the conversion step 13, the correction values L ', a', b 'corresponding to the vertex data obtained as described above are obtained.
Is converted into C, M, Y, and K values, which are control signals of the printer, and stored in the ROM 2 as vertex output values. The L, a, b → C, M, Y, and K conversions in the conversion process 13 are as follows:
C, M, Y, K using polynomials and neural networks
C, M, Y, which minimize the correction values L ', a,' b 'and the color difference by optimization, trial and error by the L, a, b simulator
This is performed by a method of searching for a combination of K or the like.

[Second Embodiment] A second embodiment of the present invention will be described with reference to FIG. FIG. 5 is an explanatory diagram of color correction according to the second embodiment of the present invention.

This embodiment is different from the first embodiment already described in the processing of the color correction step 12 shown in FIG. FIG. 5A is a view of the CIELab color space viewed from the side with the L axis vertical, and P1 is a paper forming a color hard copy under a light source for observing a color hard copy such as a d50 light source. Color of the recording material (white point on the hard copy side), P2 is the black color of the hard copy under the light source for observing the hard copy (black point on the hard copy side),
The original gray axis Ag on the hard copy side is a straight line connecting P1 and P2.

FIG. 2B is a view of the equi-brightness plane indicated by a dotted line connecting P2 and P3 in FIG. 2A as viewed from directly above (L-axis direction), and W is a light source for observing a color hard copy. Reference white of the monitor device at (the monitor side white p
A color having only the chromaticity value (a, b) of 0 int) on the isoluminance plane, and P3 indicates an arbitrary color on the same hue line as W.

In the present embodiment, in the color correction process (corresponding to the color correction process 12 of the first embodiment), the gray axes of the input color information are set to P1, P3 as shown in FIG. Are corrected so as to be a virtual gray axis Ag ′ connecting.

That is, the vertex data converted into L, a, and b in the conversion process (corresponding to the conversion process 11 in FIG. 3) is used in the color correction process (corresponding to the color correction process 12 in FIG. 3) according to the following equation. It is converted to L ', a', b '.

L ′ = L (W−L−B.L) / 100 + B. La '= a + (Wa-Ba) (L / 100) + B. a (4) b ′ = b + (W.b−B.b) (L / 100) + B. b. L, W. a, W.S. b is the coordinate value (L, a, b) of P1 in FIG. L, B. a, B. b is the coordinate value (L, a, b) of P3 in FIG.

Also in this embodiment, in the conversion process (corresponding to the conversion process 13 in FIG. 3), the correction values (L ', a', b ') corresponding to the vertices obtained as described above are used to determine the printer's The control signals are converted into C, M, Y, and K values, and the obtained data is stored in the ROM 2 as vertex output values.

[Third Embodiment] A third embodiment of the present invention will be described with reference to FIGS. FIG. 6 is an explanatory diagram of a CIELAB color space used for an input color space of the present embodiment, and FIG. 7 is a block diagram showing a configuration of a main part of the present embodiment.

In this embodiment, a color conversion is performed on color image information of a monitor device that displays a color image by a light source color, such as a TV or CRT monitor, and an input coordinate is set. Is a CIELab color space as shown in FIG. 6, and this CIELab color space is
Input coordinate values (L *, a *, b *) of the color image information of the monitor device are divided into the same unit color space cube.
, C, M, Y, and K values, which are printer control signals, are obtained from the CIELab color space. In this case, a unit color space cube including the input coordinate values of the color image information of the monitor device is selected, and linear interpolation is performed based on the output values corresponding to preset vertices of the selected unit color space cube and the input coordinate values. Are performed, and C, M,
The output values corresponding to the Y and K values are configured to be obtained.

In this embodiment, as shown in FIG. 7, an output value (C, M, Y, K) corresponding to a vertex of an input color space is stored in advance in a CPU 1A for controlling the entire operation.
M2A, RAM 3A for temporarily storing input image data,
An interpolation operation unit 5 that interpolates C, M, Y, and K values with reference to data stored in the ROM 2A based on an input signal, and converts an input image signal into an input space of an interpolation operation based on a device profile on an input side. An input signal conversion unit 6 for converting into a certain CIELab space, and a gray axis correction unit for performing color correction accompanying correction of the gray axis of the signal converted by the input signal conversion unit 6 and compression processing of the lightness component (L) are connected. Have been. The interpolation calculation unit 5 includes a C processing unit 5a for calculating a C value, an M processing unit 5b for calculating an M value, a Y processing unit 5c for calculating a Y value, and a K processing unit for calculating a K value. A processing unit 5d is provided.

The operation of the present embodiment will be described.
When 1A receives the color correction command, if the input signal is the color image information (RGB) of the monitor device, the input signal converter 6 performs RGB → XYZ → Lab conversion. The conversion in the input signal converter 6 is performed, for example, according to the equations (1) and (2) in the first embodiment.
The parameters required for this conversion are written in the device profile of the monitor device sent together with the color image information, and are converted to the Lab based on the white (Lab; 100, 0, 0) of the target monitor device. Is converted.

The input image signal (Lab) converted by the input signal conversion unit 6 is monitored on a color hard copy by the gray axis correction unit 7 by the same processing as in the equation (4) of the second embodiment. The image is color-corrected and converted into L'a'b 'so as to be displayed in the same color as the color image of the device, and is loaded into the RAM 3A.

By this color correction, the reference white of the color image of the monitor device becomes the ground white of the paper forming the color hard copy, and the black of the color image of the monitor device becomes the monitor device under the light source for observing the color hard copy. The color correction accompanying the correction of the gray axis and the compression processing of the lightness component (L) are performed so that the virtual hard copy having the same hue as the reference white of the color image becomes black.

The color information (L ') loaded into the RAM 3A
a'b ') is transferred to the interpolation calculation unit 5 and the C processing unit 5
a, M processing unit 5b, Y processing unit 5c, K processing unit 5d
, The color conversion from L'a'b 'to CMYK is performed. In this case, the coordinates (Lab) in the input space used for the interpolation calculation are L, a, b that have been subjected to compression processing by pasting in the saturation direction for colors outside the color reproduction range.
The values of C, M, Y, and K for the values are set in advance. The output values (C, M, Y,
K) is set by C using a polynomial or a neural network.
A combination of CMYK that minimizes the correction value color difference is obtained by, for example, optimization using a MYK → Lab simulator.

[Fourth Embodiment] A fourth embodiment of the present invention will be described with reference to FIG. FIG. 8 is a block diagram showing a configuration of a main part of the configuration of the present embodiment.

In this embodiment, as shown in FIG. 8, an output value (C, M, Y, K) corresponding to a vertex of the input color space is stored in advance in the CPU 1B for controlling the entire operation.
OM2B, RAM3 for temporarily storing input image data
B, an interpolation operation unit 5 that interpolates C, M, Y, and K values by referring to data stored in the ROM 2B based on the input signal;
An input signal conversion unit 6 for converting an input image signal into a CIELab space, which is an input space for an interpolation operation, based on a device profile on the input side, and color correction accompanying correction of a gray axis of the signal converted by the input signal conversion unit 6 , A gray axis correction unit 7 for performing compression processing of the lightness component (L), and a virtual gray axis setting unit 8 for adjusting and setting the chromaticity value of black of a virtual hard copy by an operator. The interpolation calculation unit 5 includes a C processing unit 5a for calculating a C value, an M processing unit 5b for calculating an M value, a Y processing unit 5c for calculating a Y value,
And a K processing unit 5d for calculating the K value.

The operation of this embodiment will be described.
When 1B receives the color correction command, if the input signal is the color image information (RGB) of the monitor device, the input signal converter 6 performs RGB → XYZ → Lab conversion. The conversion in the input signal converter 6 is performed, for example, according to the equations (1) and (2) in the first embodiment.
The parameters required for this conversion are written in the device profile of the monitor device sent together with the color image information, and are converted to the Lab based on the white (Lab; 100, 0, 0) of the target monitor device. Is converted.

The input image signal (Lab) converted by the input signal conversion unit 6 is monitored on a color hard copy by the gray axis correction unit 7 by the same processing as in the equation (4) of the second embodiment. The image is color-corrected and converted into L'a'b 'so as to be displayed in the same color as the color image of the device, and is loaded into the RAM 3B.

In this embodiment, in this case, the operator adjusts and sets an arbitrary color P3 (see FIG. 5) on the same hue line as the reference white W of the monitor device under the light source for observing the color hard copy. The reference white of the color image of the monitor device can be the background white of the paper on which the color hard copy is formed, and the black of the color image of the monitor device can be the reference white of the monitor device under the light source for observing the color hard copy. Based on the color of the same hue, the color correction accompanying the gray axis correction and the compression processing of the lightness (L) are performed so that the virtual hard copy adjusted by the operator according to the preference or the input image becomes black. You.

The color information (L ') loaded into the RAM 3A
a'b ') is transferred to the interpolation calculation unit 5 and the C processing unit 5
a, M processing unit 5b, Y processing unit 5c, K processing unit 5d
, The color conversion from L'a'b 'to CMYK is performed. In this case, the coordinates (Lab) in the input space used for the interpolation calculation are L, a, b that have been subjected to compression processing by pasting in the saturation direction for colors outside the color reproduction range.
The values of C, M, Y, and K for the values are set in advance. The output values (C, M, Y,
K) is set by C using a polynomial or a neural network.
A combination of CMYK that minimizes the correction value color difference is obtained by, for example, optimization using a MYK → Lab simulator.

[0044]

According to the first aspect of the present invention, the chromaticity value of the gray axis of the three attribute coordinates of the color is changed by the changing means in accordance with the brightness of the color image information. The conversion means converts the color image information of the monitor device that displays the color image by the light source color into the control signal of the image forming apparatus that forms the color hard copy, so that the same color as the color image of the monitor device is used. It is possible to form a color hard copy by finishing.

According to the second aspect of the present invention, the reference white of the color image of the monitor device is set to the ground white of the recording medium on which the color hard copy is formed, and the black of the color image of the monitor device is changed to the color hard copy. By changing the gray axis of the three-attribute coordinates of the color by the changing means, the color image information is set so that the virtual hard copy of the chromaticity value having the same hue as the reference white under the light source to observe is set to black. The chromaticity value is changed in accordance with the brightness of the color image information. Based on the changed chromaticity value, the converting means converts the color image information into a control signal of an image forming apparatus for forming a color hard copy. It is possible to easily form a color hard copy with the same color finish as the color image of the monitor device without the setting of.

According to the third aspect of the present invention, the changing means sets the reference white of the color image of the monitor device to the ground white of the recording medium on which the color hard copy is formed, and changes the black of the color image of the monitor device to black. The gray axis of the three attribute coordinates of the color is tilted so that the virtual hard copy having the same hue as the reference white under the light source under which the color hard copy is observed is set to black. The chromaticity value is changed in accordance with the lightness, and the color image information is subjected to a compression process by the compression means based on the changed chromaticity value. An input coordinate value to the three-dimensional input color space divided and divided into unit color space cubes is set, and a color separation component set at a vertex of the unit color space cube including the input coordinate value by interpolation calculation means Interpolation calculation of the vertex output value is performed,
The conversion means converts the color image information into a control signal of an image forming apparatus for forming a color hard copy on the basis of the interpolation calculation value. It becomes possible to form a color hard copy with the same color finish on a color image of the device.

According to the fourth aspect of the present invention, in addition to the effect obtained by the third aspect of the present invention, the chromaticity value of the virtual hard copy is selected by the selection setting means, and the color image information of the monitor device is selected. It is possible to adjust the color finish of the color hard copy, for example, by enhancing the characteristics of the hard copy.

[Brief description of the drawings]

 ■

FIG. 1 is an explanatory diagram of an RGB space used for an input color space according to a first embodiment of this invention.

FIG. 2 is a block diagram showing a configuration of a main part of the embodiment.

FIG. 3 is an explanatory diagram of a process according to the embodiment;

FIG. 4 is an explanatory diagram of color correction according to the embodiment;

FIG. 5 is an explanatory diagram of color correction according to a second embodiment of the present invention.

FIG. 6 is an explanatory diagram of a CIELAB color space used for an input color space according to a third embodiment of the present invention.

FIG. 7 is a block diagram showing a configuration of a main part of the embodiment.

FIG. 8 is a block diagram illustrating a configuration of a main part of a configuration according to a fourth exemplary embodiment of the present invention.

[Explanation of symbols]

 1, 1A, 1B CPU 2, 2A, 2B ROM 3, 3A, 3B RAM 5 Interpolation processing part 5a Processing part for C 5b Processing part for M 5c Processing part for Y 5d City part for K 6 Input signal conversion part 7 Gray Axis correction unit 8 Virtual gray axis setting unit

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI // G09G 5/02 H04N 9/79 H

Claims (4)

[Claims] 1. A color conversion device for converting color image information of a monitor device that displays a color image by a light source color into a control signal of an image forming device that forms a color hard copy, wherein the color conversion device controls the color image information according to the brightness of the color image information. Changing means for changing the chromaticity value of the gray axis of the three attribute coordinates of the color, and converting means for converting the color image information into the control signal based on the chromaticity value changed by the changing means. A color conversion device characterized by the above-mentioned. 2. A color conversion apparatus for converting color image information of a monitor device that displays a color image by a light source color into a control signal of an image forming apparatus that forms a color hard copy, wherein a reference of the color image of the monitor device is provided. White is set to the ground white of the recording medium on which the color hard copy is formed, and black of the color image of the monitor device has the same hue as the reference white under the light source for observing the color hard copy. Changing means for changing the chromaticity value according to the brightness of the color image information by inclining the gray axis of the three attribute coordinates of the color so that the virtual hard copy of the value is set to black; Converting means for converting the color image information into the control signal based on the calculated chromaticity value. 3. A color conversion device for converting color image information of a monitor device that displays a color image by a light source color into a control signal of an image forming device that forms a color hard copy, wherein a reference of the color image of the monitor device is provided. White is set to the ground white of the recording medium on which the color hard copy is formed, and black of the color image of the monitor device has the same hue as the reference white under the light source for observing the color hard copy. Changing means for changing the chromaticity value according to the brightness of the color image information by inclining the gray axis of the three attribute coordinates of the color so that the virtual hard copy of the value is set to black; Compression means for compressing the color image information based on the chromaticity value obtained; and a three-dimensional input color space having an achromatic axis and divided into the same unit color space cube. The control is performed by interpolating input coordinates of the color image information compressed by the compression unit with respect to the interval using a vertex output value of a color separation component set at a vertex of the unit color space cube including the input coordinates. A color conversion device comprising: an interpolation operation means for obtaining a signal. 4. A color conversion apparatus according to claim 3, further comprising selection setting means for selectively setting a chromaticity value of said virtual hard copy.